Cell Structure

Question 1

What is the primary function of mitochondria?

Answer 1

To carry out aerobic respiration.

Question 2

What is chromatin?

Answer 2

Chromatin is a mass of coiled threads that collect to form chromosomes during nuclear division.

Question 3

What does chromatin contain?

Answer 3

Chromatin contains DNA, which holds the genetic instructions (genes) that control cell activities, and some RNA.

Question 4

What is the main function of the nucleolus?

Answer 4

The nucleolus makes ribosomes.

Question 5

What is the largest organelle in the cell?

Answer 5

The nucleus.

Question 6

What is the outer membrane of the nuclear envelope continuous with?

Answer 6

The outer membrane is continuous with the endoplasmic reticulum.

Question 7

What do chromosomes contain?

Answer 7

Chromosomes contain DNA, the genetic material.

Question 8

What determines the size of the nucleolus?

Answer 8

The more ribosomes a cell makes, the larger its nucleolus.

Question 9

What happens to the nucleolus during nuclear division?

Answer 9

The nucleolus disappears when ribosome synthesis ceases during nuclear division.

Question 10

What is the function of the endoplasmic reticulum (ER) in transporting molecules?

Answer 10

The ER transports molecules, particularly proteins, separate from the rest of the cytoplasm.

Question 11

What is the primary function of ribosomes?

Answer 11

Ribosomes are the sites of protein synthesis.

Question 12

Where can ribosomes be found in a cell?

Answer 12

Ribosomes can be found free in the cytoplasm or attached to the RER.

Question 13

What are the functions of the SER?

Answer 13

The SER makes lipids and steroids (e.g., cholesterol, estrogen, and testosterone), stores calcium ions, and is involved in drug metabolism.

Question 14

What role does SER play in muscle cells?

Answer 14

SER is abundant in muscle cells because it stores calcium ions, which are involved in muscle contraction.

Question 15

What is the function of SER in the liver?

Answer 15

In the liver, SER is involved in drug metabolism.

Question 16

What types of molecules are synthesized by the SER?

Answer 16

The SER synthesizes lipids and steroids, such as cholesterol and reproductive hormones like estrogen and testosterone.

Question 17

What is the Golgi apparatus?

Answer 17

The Golgi apparatus is a stack of flattened sacs called cisternae, involved in processing and packaging molecules like proteins and lipids.

Question 18

How is the Golgi apparatus formed and broken down?

Answer 18

It is formed at one end from vesicles budding off from the ER and broken down at the other end to form Golgi vesicles.

Question 19

What are the functions of the Golgi apparatus?

Answer 19

The Golgi apparatus processes and collects molecules, particularly proteins from the RER, and transports them in Golgi vesicles either within the cell or out of the cell.

Question 20

What are some examples of functions of the Golgi apparatus?

Answer 20

1. Making lysosomes using Golgi vesicles.
2. Adding sugars to proteins to form glycoproteins.
3. Adding sugars to lipids to form glycolipids.
4. Synthesizing new cell walls during plant cell division.
5. Releasing mucin (a main component of mucus) in goblet cells.

Question 21

What are glycoproteins and glycolipids, and why are they important?

Answer 21

Glycoproteins and glycolipids are molecules made by adding sugars to proteins or lipids. They are important components of membranes and play key roles in cell signaling.

Question 22

What are Golgi vesicles, and what do they do?

Answer 22

Golgi vesicles are formed from the Golgi apparatus and transport processed molecules to other parts of the cell or for secretion out of the cell.

Question 23

Where are lysosomal enzymes synthesized, and how are they delivered to lysosomes?

Answer 23

Lysosomal enzymes are synthesized on the RER and delivered to lysosomes via the Golgi apparatus.

Question 24

Besides energy production, what is another function of mitochondria?

Answer 24

Mitochondria are involved in the synthesis of lipids.

Question 25

What are microtubules, and where are they found?

Answer 25

Microtubules are long, rigid, hollow tubes found in the cytoplasm.

Question 26

What are the mechanical and transport functions of microtubules?

Answer 26

1. Provide mechanical support to the cell. 2. Form an intracellular transport system for moving secretory vesicles and organelles, such as during exocytosis. 3. Microtubules form part of the structure of centrioles. 4. Microtubules form an essential part of the mechanism involved in the beating movements of cilia and flagella. 5. During nuclear division, a spindle made of microtubules is used for the separation of chromatids or chromosomes.

Question 27

How are microtubules involved in nuclear division?

Answer 27

Microtubules form the spindle used for the separation of chromatids or chromosomes during nuclear division.

Question 28

What is a centriole, and what is its function?

Answer 28

A centriole is a hollow cylinder that acts as a microtubule organizing center (MTOC) and is needed for the production of cilia. It also produces spindle fibres.

Question 29

What properties of cellulose fibers make them ideal for providing support?

Answer 29

Cellulose fibers are inelastic and have high tensile strength, making them difficult to break by pulling on each end.

Question 30

What are the main functions of cell walls in plants?

Answer 30

1. Provide mechanical strength and support to individual cells and the plant as a whole. 2. Prevent cells from bursting by osmosis when surrounded by a solution with a higher water potential. 3. Determine the shapes of cells during growth through the orientation of cellulose fibers.

Question 31

Which cell organelles have double membrane?

Answer 31

1. Nucleus 2. Mitochondria 3. Chloroplasts

Question 32

Which cell organelles have single membrane?

Answer 32

1. Vacuoles 2. Lysosomes 3. Endoplasmic Reticulum 4. Golgi Apparatus

Question 33

Describe the structure of a virus.

Answer 33

1. A molecule of DNA 2. A protein coat called a capsid 3. (some viruses only) a membrane-like outer layer, called the envelope, that is made of phospholipids.

Question 34

Why are all viruses considered parasitic?

Answer 34

Viruses are parasitic because they can only reproduce by infecting and taking over living cells. Their DNA or RNA hijacks the host cell’s protein-synthesizing machinery to produce new virus particles.

Question 35

Which structures are always present in a bacterium?

Answer 35

1. Cell wall 2. Cell surface membrane 3. Cytoplasm 4. Circular DNA 5. Ribosomes

Question 36

Which structures are sometimes present in a bacterium?

Answer 36

1. Flagellum 2. Capsule or slime layer 3. Infolding of cell surface membrane 4. Plasmid 5. Pili

Question 37

Describe the structure of a bacterium.

Answer 37

1. Cell wall made from peptidoglycan. Prevents the cell from bursting when water enters by osmosis. 2. Cytoplasm - does not contain any double membrane bound organelles. 3. Circular DNA - Found in the nucleoid, also contains proteins and small amounts of RNA. Not surrounded by a double membrane. 4. Flagellum for locomotion - does not bend. 5. Infolding of cell surface membrane - may form a photosynthetic membrane or carry out nitrogen fixation. 6. Capsule - help the bacterium from drying out. Helps protect bacteria from antibiotics. 7. Plasmid - small circle of DNA. Contains only a few genes that give resistance to antibiotics. 8. Pili - used for attachment to other cells or surfaces. Allow the transfer of genes.

Question 38

State differences between electron and light microscope.

Answer 38

Light Microscope - resolution of lower than electron microscope (200 nm) - magnification is lower (1500) - uses glass lens - living and nonliving organisms can be seen - usually coloured image is formed - no vacuum is needed - less expensive Electron Microscope - resolution is higher than light microscope (0.5 nm) - magnification is higher (250000) - uses electromagnets - only nonliving organisms can be seen - black and white image is formed - expensive

Question 39

Why is a vacuum needed in an electron microscope?

Answer 39

Electrons cannot be focused without a vacuum as they will collide with air molecules and scatter. 

Question 40

State functions of the cell surface membrane. 

Answer 40

1. protects the cell 2. partially permeable 3. transport of proteins 4. allows fats, fat soluble vitamins, water, non-polar substances, gases and fatty acids 5. does not allow glucose, polar ions and amino acids 6. cell recognition - has antigens which helps the cell to recognise this self from non-self 7. cell signalling - has receptors which have a complimentary shape to the hormone or signalling molecule. This by just attaching to the receptor the signal is passed on to the cell to produce the effect

Question 41

State functions of the nucleus. 

Answer 41

1. all cell activities are controlled by the nucleus 2. helps in protein synthesis by sending message (mRNA) to the ribosomes through nuclear pore 3. mitosis/cell division 4. nucleolus makes ribosomes

Question 42

What is the function of lysozyme?

Answer 42

breakdown/digestion of unwanted structures e.g old organelles

Question 43

State the function of chloroplast. 

Answer 43

- site for photosynthesis - ATP produced here